Arfa Daily wrote in message
...


"N_Cook" wrote in message
...
Arfa Daily wrote in message
...


"whit3rd" wrote in message
...
On Tuesday, February 12, 2013 12:31:27 AM UTC-8, N_Cook wrote:
Arfa Daily wrote in message

...

I have a current transformer on one leg of the input to my dummy
load
/
power meter. This allows me to monitor ...

I suspect a current transformer would affect any PA/speaker/Zobell
resonance/interaction effect.

A properly loaded currrent transformer can be ten millliohms, or a
few
hundred microohms. There needn't be any significant effect on the
system
being measured.


Quite. The one that I use is completely non-invasive to the system it's
monitoring - in this case an output stage into a dummy load. It's just
a
fully encapsulated winding with a hole through the middle. One leg of
the
input to my tester passes through this hole. The winding is terminated
with
a couple of k, and my scope hooks directly across it, fully isolated
from
the unit under test. It has zero measurable effect on the amplifier or
any
networks connected in the amp's output circuit. I would not have
designed
it
in, and been using it without issue for some years, if it did ...

This is the exact one



http://ww.sourcingmap.co.uk/020a-inp...edding-precisi
on-current-transformer-ta17-p-133281.html

Arfa



So you would pass a speaker lead through the hole, ignoring the primary
sense turns.
In the meantime I may as well try a solenoid without pole piece


Yes, a speaker lead passes straight through the middle. In this use of the
device, there is no 'primary sense turns' issue. The wire passing through
the middle represents a single turn primary. With the ratio being 2000:1,
that provides a more than adequate output level for really very small
power
levels - just a few watts in fact. I dare say that if you were bothered,
you
could rectify the voltage appearing across the secondary, and hang a
suitable meter and calibration pot across the output, and get a fair
indication of relative, if not absolute power levels. The transformer is
rated to 20A, which I believe is the point at which the core starts to
saturate, so the output becomes non-linear, rather than where anything
nasty
starts to happen. 20A allows a pretty powerful amp to be run through it.

You can try a solenoid. I'm sure that you will get something out, but I'm
not sure how much. CTs are usually torroidal in construction - at least
the
small ones that I've seen - and I guess there's a reason for that. I mean,
at the end of the day, you can drink coffee out of a shoe, but a cup works
better ... :-)

Arfa


I tried a solenoid but not enough output and poor at sub 100Hz. Do you know
what the response is like below 100Hz on your pass-thru Tx ?
Dug out a couple of microphone Tx and checked they worked down to 40Hz ,
taking readings, less response but not too much. Then some more important
jobs came in.
One for the phones out line ( so same f response) and one with series 1K or
so over the speaker, should work fed to a normal dual channel scope